Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $106.95   6.550%   $113.9552   $113.96   $113.95   $114.00  
  Purchase #2 $16.28   3.295%   $16.8164   $16.82   $16.80   $16.80  
  Purchase #3 $217.87   7.355%   $233.8943   $233.89   $233.90   $233.90  
  Purchase #4 $215.45   7.405%   $231.4041   $231.40   $231.40   $231.40  
  Purchase #5 $158.37   9.861%   $173.9869   $173.99   $174.00   $174.00  
  Purchase #6 $45.99   11.208%   $51.1446   $51.14   $51.15   $51.10  
  Purchase #7 $118.40   7.137%   $126.8502   $126.85   $126.85   $126.90  
  7 purchase totals = $879.31       $948.0517   $948.05   $948.05   $948.10